Multistage Fiber Filtering Apparatus Capable of Selectively Filtering

ABSTRACT

The present invention relates to a multistage fiber filtering apparatus capable of selectively filtering depending on turbidity of raw water, in which a first filtration mode where the raw water passes through a fiber ball medium, a second filtration mode where the raw water passes through a fiber yarn medium, or a third filtration mode where the raw water passes through both of the fiber yarn medium and the fiber ball medium may be selectively operated.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority to Korean Patent Application No.10-2016-0078018, filed on Jun. 22, 2016, the disclosure of which isincorporated herein by reference in its entirety.

BACKGROUND OF THE INVENTION Field of the Invention

Exemplary embodiments of the present invention relate to a multistagefiber filtering apparatus and, more particularly, to a multistage fiberfiltering apparatus capable of selectively filtering depending onturbidity of raw water.

Description of the Related Art

In general, a filtering apparatus which filters contaminated raw waterby using a filter to make the contaminated raw water clean treated waterand supply it has been widely used not only for drinking water but alsofor treatment of water and sewage or factory water. In particular, thefiltering apparatus used for treatment of river water or factorywastewater or seawater desalination facilities is becoming larger andlarger in order to increase the water quantity to be treated and improvewater quality.

There is a multi type filtering apparatus that is used for thelarge-capacity water treatment applications. For example, Korean PatentNo. 10-0438460 entitled “Multi type air gap controlling fiber filter”can be referred for teaching such.

In addition, as a method used in existing water purification plants,water treatment plants, or seawater desalination plants, there is amethod for filtering water produced from the filter again using acartridge filter separately installed, which requires a lot ofinstallation sites and costs. In summary, in the above case, there is aproblem in that the occupied space or the installation space becomesvery large and thus a lot of site is required or cost is increased.

Accordingly, in order to improve the treating speed and improve thewater quality, a plurality of filters are used or a plurality of stages(multi stages) are arranged in the same filtration tank. For example,Korean Patent No. 10-0898122 entitled ‘Vertical multistage link typepore control fiber filter’ is disclosed.

In the existing vertical multistage link type pore control fiber filter,if an air gap controlling fiber filter medium is formed in a filtrationtank around a strainer so that raw water in the filtration tank passesthrough the fiber filter medium to be introduced into the strainer, aplurality of unit fiber filters draining the raw water to a lower end ofthe strainer are vertically stacked by making lower ends of the strainerof the respective unit fiber filters communicate with upper ends of thefiltration tank of the respective lower unit fiber filters, thefiltration tank of an uppermost unit fiber filter is provided with a rawwater inlet through which external raw water is introduced, and thelower end of the strainer of a lowermost unit fiber filter communicateswith a filtered water discharge pipe to drain filtered water to anexternal water tank.

At this time, the vertical multistage link type pore control fiberfilter has a structure in which the raw water is introduced through theraw water inlet pipe 11 formed at an uppermost end of a filtration tank10, passes through all multistage fiber media 20, and then is dischargedthrough a filtered water discharge pipe 12 formed at a lowermost end ofthe filtration tank 10.

However, the quality of the raw water to be treated is variable. Inparticular, the fluctuation in the quality of the raw water is verylarge during summer and rainfall, and therefore the raw water cannot butunnecessarily pass through all the fiber media even if the raw waterneed not be subjected to the multistage filtration all the time.

RELATED ART DOCUMENT Patent Document

Korea Patent No. 10-0898122 (May 11, 2009)

SUMMARY OF THE INVENTION

The present invention provides a multistage fiber filtering apparatuscapable of selectively filtering depending on turbidity of raw water.

Other aspects of the present invention can be understood by thefollowing description, and become apparent with reference to theembodiments of the present invention. Also, it is obvious to thoseskilled in the art to which the present invention pertains that benefitsof the present invention can be realized by the means as claimed andcombinations thereof.

In accordance with one aspect of the present invention, a multistagefiber filtering apparatus comprises: an enclosure configured to includean upper box and a lower box communicating with the upper box; astrainer configured to be installed in the upper box along alongitudinal direction; a plurality of fiber yarn media configured to befixed to upper and lower fixing means, each of the upper and lowerfixing means coupled to upper and lower portions of the strainer, toform a first filtering layer while surrounding an outer circumferentialsurface of the strainer; and a plurality of fiber ball media configuredto be built in the lower box to form a second filtering layer; wherein afirst filtration mode, raw water passing through the fiber ball medium;a second filtration mode, the raw water passing through the fiber yarnmedium; or a third filtration mode, the raw water passing through bothof the fiber yarn medium and the fiber ball medium, may be selectivelyoperated depending on turbidity of the raw water.

The multistage fiber filtering apparatus may further include: aturbidity meter configured to measure the turbidity of the raw water.

When the turbidity measured by the turbidity meter is low, the raw watermay be filtered by the first filtration mode; when the turbiditymeasured by the turbidity meter is medium, the raw water may be filteredby the second filtration mode; and when the turbidity measured by theturbidity meter is high, the raw material may be filtered by the thirdfiltration mode.

The multistage fiber filtering apparatus may further include: a firstpipe configured to be formed on one side wall of a lower portion of theupper box and introduce the raw water; a second pipe configured to beformed on one side wall of a lower portion of the lower box anddischarge filtered water; and a third pipe configured to be formed onone side wall of an upper portion of the lower box and introduce the rawwater or discharge the filtered water.

In the first filtration mode, the raw water may be introduced throughthe third pipe to pass through the fiber ball medium and then bedischarged through the second pipe.

In the second filtration mode, the raw water may be introduced throughthe first pipe to pass through the fiber yarn medium and then bedischarged through the third pipe.

In the third filtration mode, the raw water may be introduced throughthe first pipe to sequentially pass through the fiber yarn medium andthe fiber ball medium and then be discharged through the second pipe.

The first pipe may include: a raw water inlet pipe configured to beprovided with a raw water inlet control valve controlling an introducedamount of raw water; and a backwashing water discharge pipe configuredto be provided with a backwashing water discharge control valveregulating a discharged amount of backwashing water.

The multistage fiber filtering apparatus may further include: a firstair inlet pipe configured to be connected to one side of the second pipeto introduce air during backwashing.

The multistage fiber filtering apparatus may further include: a secondair inlet pipe configured to be connected to one side of the third pipeto introduce air during backwashing.

The multistage fiber filtering apparatus may further include: an airdischarge pipe configured to be formed on an upper surface of the upperbox to discharge air.

The multistage fiber filtering apparatus may further include: acontroller configured to selectively introduce the raw water into thefirst pipe or the third pipe depending on the turbidity measured by theturbidity meter.

The controller may control the raw water to be introduced through thethird pipe when the turbidity measured by the turbidity meter is lowturbidity and control the raw water to be introduced through the firstpipe when the turbidity is medium turbidity or high turbidity.

A part of the second pipe may be provided with a second pipe controlvalve for determining a discharged amount of the filtered water.

A part of the third pipe may be provided with a third pipe control valvefor determining the introduced amount of raw water or the dischargedamount of filtered water.

The controller may control the third pipe control valve and the secondpipe control valve to be open when the raw water is of low turbidity sothat the raw water is filtered by the first filtration mode.

The controller may control a control valve, which is disposed in thefirst pipe, to regulate an introduced amount of raw material. When theraw water is of medium turbidity, the controller may control the thirdpipe control valve to be open and may control the second pipe controlvalve to be closed to filter the raw water by the second filtrationmode.

When the raw water is of high turbidity, the controller may control thesecond pipe control valve to be open and may control the third pipecontrol valve to be closed to filter the raw water by the thirdfiltration mode.

A distribution plate provided with a plurality of distribution groovesmay be installed between the upper box and the lower box.

A lower end of the upper box may be provided with a swash plate reachingfrom a lower end of the strainer to an outer surface of the lower boxalong a circumferential direction.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other features of the present invention will be moreclearly understood from the following detailed description taken inconjunction with the accompanying drawings, in which:

FIG. 1 is a cross-sectional view illustrating an existing verticalmultistage link type pore control fiber filter;

FIG. 2 is a cross-sectional view of a multistage fiber filteringapparatus according to an embodiment of the present invention;

FIG. 3 is a cross-sectional view illustrating a 1-stage filteringoperation of a fiber ball medium in the multistage fiber filteringapparatus of FIG. 2;

FIG. 4 is a cross-sectional view illustrating the 1-stage filteringoperation of a fiber yarn medium in the multistage fiber filteringapparatus of FIG. 2;

FIG. 5 is a cross-sectional view illustrating a 2-stage filteringoperation of a fiber yarn medium and a fiber ball medium in themultistage fiber filtering apparatus of FIG. 2; and

FIG. 6 is a diagram illustrating a distribution plate of FIG. 2separately.

DESCRIPTION OF SPECIFIC EMBODIMENTS

Hereinafter, a multistage fiber filtering apparatus capable ofselectively filtering according to an exemplary embodiment of thepresent invention will be described with reference to FIGS. 2 to 6.

Further, terms to be described below are terms defined in considerationof the functions of the present invention, which may be changeddepending on user's or operator's intentions or practices. The followingembodiments do not limit the scope of the present invention but are onlyexemplary matters of components proposed in the claim of the presentinvention.

A part irrelevant to the description will be omitted to clearly describethe present invention, and the same elements will be designated by thesame reference numerals throughout the specification. In the presentspecification, unless explicitly described to the contrary, “comprising”any components will be understood to imply the inclusion of othercomponents rather than the exclusion of any other elements.

FIG. 2 is a cross-sectional view of a multistage fiber filteringapparatus according to an embodiment of the present invention, FIG. 3 isa cross-sectional view illustrating a 1 stage filtering operation of anfiber ball medium in the multistage fiber filtering apparatus of FIG. 2,FIG. 4 is a cross-sectional view illustrating the 1-stage filteringoperation of the fiber yarn medium in the multistage fiber filteringapparatus of FIG. 2, FIG. 5 is a cross-sectional view illustrating a2-stage filtering operation of the fiber yarn medium and the fiber ballmedium in the multistage fiber filtering apparatus of FIG. 2, and FIG. 6is a diagram illustrating a distribution plate of FIG. 2 separately.

In the description of embodiments of the present invention, raw waterrefers to a fluid before being introduced into a multistage fiberfiltering apparatus of the present invention for filtration, andfiltered water refers to a fluid discharged from the multistage fiberfiltering apparatus of the present invention in the filtered state.

However, the term is not limited thereto, and the raw water may bereferred to as filtered water, treated water, discharged water, or thelike, with changing a name depending on a moving route or a movingstate.

First, a multistage fiber filtering apparatus according to an embodimentof the present invention will be described with reference to FIG. 2.

The multistage fiber filtering apparatus according to an embodiment ofthe present invention may be configured to largely include an enclosure10 including an upper box 100 and a lower box 200 communicating with theupper box 100, a strainer 120, a plurality of fiber yarn media 140forming a first filtering layer, a plurality of fiber ball media 220forming a second filtering layer, a first pipe 300, a second pipe 400,and a third pipe 500.

The enclosure 10 is formed in a multi-layered structure and includes thelower box 200 installed at a bottom and the upper box 100 installed atan upper portion of the lower box 200. The upper box 100 and the lowerbox 200 may be preferably formed as a cylindrical body and may have thesame diameter. Further, the upper box 100 and the lower box 200 arecommunicated with each other and may be integrally formed according tothe embodiment.

One side of the lower portion of the upper box 100 is connected to thefirst pipe 300 into which raw water is introduced during filtration. Thefirst pipe 300 may not only be provided with water during filtration butmay also discharge backwashing water during backwashing. However, thepresent invention is not limited thereto, and a pipe for dischargingbackwashing water may be separately provided on the other side of thelower portion of the upper box 100.

In the present embodiment, the first pipe 300 includes a raw water inletpipe 320 provided with a raw water inlet control valve 322 forregulating an introduced amount of raw water, and a backwashing waterdischarge pipe 340 provided with a backwashing water discharge controlvalve 342 for regulating a discharged amount of backwashing water. Inthis way, a location where the raw water is introduced during filtrationand a location where the backwashing water is discharged may beseparated from each other. The introduced amount of raw water may beregulated by the raw water inlet control valve 322 to prevent the rawwater from being introduced, and the discharged amount of backwashingwater may be regulated by the backwashing water discharge control valve342 to prevent a fluid in the upper box 100 from being discharged.

A second pipe 400 for discharging filtered water during filtration isconnected to one side of the lower side of the lower box 200. The secondpipe 400 may not only be provided with filtered water during filtrationbut also introduced with backwashing water during backwashing.

A portion of the second pipe 400 may be provided with a second pipecontrol valve 402 to determine the discharged amount of filtered wateror the introduced amount of washing water.

Further, a first air inlet pipe 420 connected to one side of the lowerbox 200 or one side of the second pipe 400 to introduce air duringbackwashing may be formed. A part of the first air inlet pipe 420 may beprovided with a first air inlet control valve 422 to control theintroduced amount of air.

One side of the upper portion of the lower box 200 is connected to athird pipe 500 for introducing raw water or discharging filtered waterduring filtration. The third pipe 500 may not only introduce raw wateror discharge filtered water during filtration but may also introducebackwashing water during backwashing.

A part of the third pipe 500 may be provided with a third pipe controlvalve 502 to determine the introduced amount of raw water or thedischarged amount of filtered water.

Further, a second air inlet pipe 520 connected to one side of the upperportion of the lower box 200 or one side of the third pipe 500 tointroduce air during backwashing may be formed. A part of the second airinlet pipe 520 may be provided with a second air inlet control valve 522to control the introduced amount of air.

In addition, an upper surface of the upper box 100 may be provided withan air discharge pipe 600 for discharging air. Accordingly, the airintroduced during the backwashing may be easily discharged through anuppermost air discharge pipe 600.

The strainer 120 is installed inside the upper box 100 along alongitudinal direction, and an upper side of the strainer is closed anda lower side thereof is open. The strainer 120 may preferably be formedas a long cylindrical tube, and a side wall portion of the strainer 120may be densely provided with a plurality of holes so that air or watermay be introduced and discharged.

The plurality of fiber yarn media 140 are formed on an outer sidesurface of the strainer 120 along the longitudinal direction to form afirst filtering layer. An upper end of the fiber yarn medium 140 isfixed to an upper fixing means 142 coupled to the upper portion of thestrainer 120 and a lower end of the fiber yarn medium 140 may be fixedto a lower fixing means 144 coupled to the lower portion of the strainer120.

The plurality of fiber yarn media 140 are evenly disposed along acircumferential direction to cover all the side portions of the strainer120. Further, to make a filtering path of raw water long, the fiber yarnmedium 140 may be formed in multiple plies to make the first filteringlayer thick.

The fiber yarn medium 140 is formed as a bundle of fiber yarns, in whichmaterials of the fiber yarn may be flexible materials such as polyester,polypropylene, and polyamide. Further, when ion filtration or the likeis required depending on applications, the material of the fiber yarnmay also be conductive fiber yarns such as polyethylene or polystyrene.

The fiber yarn medium 140 may be pressed or loosened along alongitudinal direction, and thus an air gap of the fiber yarn medium 140may be regulated. For this purpose, the upper fixing means 142 may beinstalled so as to be movable up and down by a separate driver. That is,if the upper fixing means 142 moves upward, the fiber yarn medium 140 ispulled and pressed on the strainer 120 to reduce a size of the air gapand if the upper fixing means 142 moves downward, the fiber yarn medium140 has a reduced tension force and is loosed to increase the size ofthe air gap.

A distribution plate 160 may be installed between the upper box 100 andthe lower box 200. Referring to FIGS. 2 and 6, a disc-shaped body of thedistribution plate 160 is provided with a plurality of distributiongrooves 162 having a uniform size, and the filtered water passingthrough the fiber yarn medium 140 and the strainer 120 is evenlydispersed and put in the lower housing 200.

A backwashing nozzle unit 122 may be provided under the strainer 120.The backwashing nozzle unit 122 may inject air, which is introduced intothe upper portion of the lower box 200 through the second air inlet pipe520, upward and the air and water injected upward shake the lowerportion of the fiber yarn medium 140. Accordingly, the fiber yarn medium140 is rubbed by the backwashing water and the air, thereby moreefficiently performing washing.

Meanwhile, the lower end of the upper box 100 may be provided with aswash plate 102 reaching from the lower end of the strainer 120 to anouter surface of the lower box 200 along a circumferential direction sothat primarily filtered water discharged from the strainer is widelydispersed to an outside of the lower box 200 and put therein. That is,the swash plate 102 is formed in the form of a truncated cone whenviewed from a sectional view. Accordingly, a part of the filtered waterpassing through the fiber yarn medium 140 may flow along an innersurface of the swash plate 102 and then may be put in the lower box 200through the distribution plate 160.

The plurality of fiber ball media 220 are provided inside the lower box200 to form the second filtering layer. The fiber ball medium 220 is aspherical porous filter made of cotton or the like and serves tosecondarily filter the primarily filtered water passing through thefiber yarn media 140 and the strainer 120 of the upper box 100. Thefiber ball medium 220 may include a rigidly formed core portion and atarget portion connected to the core portion to form a thick fiber layerand may be formed to have a diameter ranging from approximately 10 to 50mm.

In addition, a lower surface of the lower box 200 includes a centralportion formed as a flat plate and an outer portion formed as aninclined surface, in which the central portion may be provided with aplurality of strainer nozzles 240. The strainer nozzle 240 injects airor washing water upward so that the fiber ball media 220 may be mixedwith each other. Therefore, when air or water is jetted from thestrainer nozzle 240, a circulation flow is formed upward from thecentral portion and downward from the outer portion, such that the fiberball media 220 may be evenly washed while being smoothly mixed with eachother, and a surface layer of the second filtering layer may bearbitrarily located while being mixed with the plurality of fiber ballmedia 220, thereby effectively keeping the filtration performance for along period of time.

In the multistage fiber filtering apparatus of the present invention, afirst filtration mode passing through the fiber ball medium 220, asecond filtration mode passing through the fiber yarn medium 140, or athird filtration mode passing through both of the filter yarn medium 140and the fiber ball medium 220 is selectively operated depending on theturbidity of raw water.

To this end, a turbidity meter 700 for measuring the turbidity of theraw water may be further provided.

Accordingly, when the turbidity measured by the turbidity meter 700 islow turbidity, the raw water is filtered by the first filtration mode;when the turbidity is medium turbidity, the raw water is filtered by thesecond filtration mode; and when the turbidity is high turbidity, theraw water is filtered by the third filtration mode.

Next, the filtering operations according to the first to thirdfiltration modes of the multistage fiber filtering apparatus accordingto the embodiment of the present invention will be described in detailwith reference to FIGS. 3 to 5.

The first filtration mode is a mode filtered only by the fiber ballmedium 220 when the raw water has low turbidity and does not passthrough the fiber yarn medium 140. As illustrated in FIG. 3, in thefirst filtration mode, the raw water is introduced through the thirdpipe 500 to pass through the fiber ball medium 220, and is filtered andthen discharged as filtered water through the second pipe 400. At thistime, the third pipe control valve 502 is open to introduce the rawwater, and the second pipe control valve 402 is also open to dischargethe filtered water.

Further, the second filtration mode is a mode filtered only by the fiberyarn medium 140 when the raw water has medium turbidity and does notpass through the fiber ball medium 220. In detail, as illustrated inFIG. 4, in the second filtration mode, the raw water is introducedthrough the first pipe 300, and in the present embodiment, is introducedthrough the raw water inlet pipe 320. To this end, the raw water inletcontrol valve 322 is kept in an open state. At this time, the raw watermay be pressurized by a pump (not shown) formed on the outside of theraw water inlet pipe 320 and may be introduced into the upper box 100,and a height of the raw water stored in a space between the upper box100 and the strainer 120 is increased by water pressure.

The raw water passes through the first filtering layer formed of thefiber yarn medium 140 and is filtered, and is then introduced into thestrainer 120 through a through hole of the strainer 120. In this way,the filtered water filtered by the fiber yarn medium 140 flows downwardor drops along an inner wall of the strainer 120 and an inner wall ofthe swash plate 102 to reach the distribution plate 160. Next, thefiltered water may be introduced into the lower box 200 through theplurality of distribution grooves 162 formed on the distribution plate160. At this time, the second pipe control valve 402 is kept in a closedstate and the third pipe control valve 502 is kept in an open state,such that the filtered water is not discharged through the second pipe400 via the fiber ball medium 220 but is discharged through the thirdpipe 500. At this time, since the second pipe control valve 402 is keptin the closed state, as the filtered water or the treated water that hasbeen treated when it is operated in the existing filtration mode isconverted into the second filtration mode, a water level of the filteredwater or the treated water may remain inside the lower box 200 whilebeing retained.

The third filtration mode filters raw water by sequentially passing theraw water through the fiber yarn medium 140 and the fiber ball medium220 when the raw water has high turbidity, and therefore has anincreased filtration time and filtration amount.

In detail, as illustrated in FIG. 5, in the third filtration mode, theraw water is introduced through the first pipe 300, and in the presentembodiment, is introduced through the raw water inlet pipe 320. To thisend, the raw water inlet control valve 322 is kept in an open state. Atthis time, the raw water may be pressurized by a pump (not shown) formedon the outside of the raw water inlet pipe 320 and may be introducedinto the upper box 100, and a height of the raw water stored in a spacebetween the upper box 100 and the strainer 120 is increased by waterpressure.

The raw water passes through the first filtering layer formed of thefiber yarn medium 140 and is primarily filtered, and is then introducedinto the strainer 120 through a through hole of the strainer 120. Inthis way, the filtered water primarily filtered by the fiber yarn medium140 flows downward or drops along the inner wall of the strainer 120 andthe inner wall of the swash plate 102 to reach the distribution plate160. Next, the filtered water may be introduced into the lower box 200through the plurality of distribution grooves 162 formed on thedistribution plate 160 and evenly distributed on the surface layer ofthe second filtering layer made of the fiber ball medium 220.

At this time, since the second pipe control valve 402 is kept in theopen state and the third pipe control valve 502 is kept in the closedstate, the primarily filtered water is not discharged through the thirdpipe 500 but instead passes through the second filtering layer made ofthe fiber ball medium 220 within the lower box 200 and is secondarilyfiltered. The filtered water, which has been subjected to the secondaryfiltration, is discharged through the second pipe 400.

As described above, in the multistage fiber filtering apparatus of thepresent invention, the 1-stage filtration of the fiber yarn medium 140,the 1-stage filtration of the fiber ball medium 220, or the 2-stagefiltration of the fiber yarn medium 140 and the fiber ball medium 220may be selectively performed depending on the turbidity of the rawwater, such that the use of each fiber filter medium can be reduced,thereby making the replacement cycle long and reducing the maintenancecost.

In addition, the amount of backwashing water can be reduced due to thechange of the filtration mode, such that the burden of wastewatertreatment in the backwashing water treatment apparatus, which is thesubsequent process, can be reduced and the drug consumption and theamount of sludge can be reduced.

A multistage fiber filtering apparatus according to another embodimentof the present invention may further include a controller 800controlling raw water to be selectively introduced through the firstpipe 300 or the third pipe 500 depending on the turbidity measured bythe turbidity meter 700.

The controller 800 may be connected to the turbidity meter 700 to besupplied with the turbidity of raw water measured by the turbidity meter700. Thereby, the controller 800 controls the raw water to be introducedthrough the third pipe 500 if the turbidity of raw water is the lowturbidity and may control the raw water to be introduced through thefirst pipe 300 if the turbidity of the raw water is the medium or highturbidity.

At this time, a predetermined value may be input as a reference valuefor dividing the raw water into low turbidity, medium turbidity, andhigh turbidity.

Specifically, when the raw water is of low turbidity, the controller 800controls the third pipe control valve 502 to be open so that the rawwater may be introduced through the third pipe 500, and also controlsthe second pipe control valve 402 to be open so that the treated waterfiltered by passing through the fiber ball medium 220 may be dischargedthrough the second pipe 400.

When the raw water is of medium turbidity, the controller 800 controlsthe raw water inlet control valve 322 to be open so that the raw watermay be introduced through the first pipe 300 and the raw water inletpipe 320 in the present embodiment and controls the third pipe controlvalve 502 to be open so that the filtered water filtered by passingthrough the fiber yarn medium 140 may be discharged through the thirdpipe 500, and, at the same time, controls the second pipe control valve402 to be closed so that the filtered water is not discharged throughthe second pipe 400.

Further, when the raw water is of high turbidity, the controller 800 maycontrol the raw water inlet control valve 322 to be open so that the rawwater may be introduced through the first pipe 300 and the raw waterinlet pipe 320 in the present embodiment and may control the second pipecontrol valve 402 to be open simultaneously with controlling the thirdpipe control valve 502 to be closed so that the filtered water primarilyfiltered by passing through the fiber yarn medium 140 may be introducedinto the lower box 200 to pass through the fiber ball medium 220 and maybe secondarily filtered to be discharged through second pipe 400.

Next, in the multistage fiber filtering apparatus according to anembodiment of the present invention, the backwashing operation will bedescribed below.

The multistage fiber filtering apparatus according to an embodiment ofthe present invention may also perform the backwashing operation by thefirst and second backwashing modes.

The first backwashing mode may be performed when both the fiber yarnmedium 140 and the fiber ball medium 220 need to be backwashed. Thefiber ball medium 220 may be primarily washed by the washing waterintroduced through the second pipe 400 at the lower portion of the lowerbox 200, and the fiber yarn medium 140 is secondarily washed by thewashing water of which the water level rises and then the backwashingwater may be discharged through the first pipe 300 at the lower portionof the upper box 100.

Further, the second backwashing mode is performed only when thebackwashing of the fiber yarn medium 140 is required, and the fiber yarnmedium 140 is washed by the washing water introduced through the thirdpipe 500 at the upper portion of the lower box 200 and then thebackwashing water may be discharged through the first pipe 300 at thelower portion of the upper box 100.

According to the multistage fiber filtering apparatus capable ofselectively filtering, it is possible to selectively operate the 1-stagefiltration of the fiber yarn medium, the 1-stage filtration of the fiberball medium, or the 2-stage filtration of the fiber yarn medium and thefiber ball medium depending on the turbidity of the raw water.

As a result, the use of each fiber filter media may be reduced and thereplacement period is long, such that the maintenance cost can bereduced.

In addition, the amount of backwashing water can be reduced due to thechange of the filtration mode, such that the burden of wastewatertreatment in the backwashing water treatment apparatus, which is thesubsequent process, can be reduced and the drug consumption and theamount of sludge can be reduced.

It should be understood that the effects of the present invention arenot limited to the effects described above, but include all effects thatcan be deduced from the detailed description of the present invention orthe configurations of the invention described in the claims. The presentinvention is not limited to the above-described specific embodiments anddescriptions, and various modifications can be made to those skilled inthe art without departing from the gist of the present invention claimedin the claims and the modifications are within the scope of protectionof the present invention.

What is claimed is:
 1. A multistage fiber filtering apparatus,comprising: an enclosure configured to include an upper box and a lowerbox communicating with the upper box; a strainer configured to beinstalled in the upper box along a longitudinal direction; a pluralityof fiber yarn media configured to be fixed to upper and lower fixingmeans, each of the upper and lower fixing means coupled to upper andlower portions of the strainer, to form a first filtering layer whilesurrounding an outer circumferential surface of the strainer; and aplurality of fiber ball media configured to be built in the lower box toform a second filtering layer; wherein a first filtration mode of rawwater passing through the fiber ball medium, a second filtration mode ofthe raw water passing through the fiber yarn medium, or a thirdfiltration mode of the raw water passing through both of the fiber yarnmedium and the fiber ball medium, is selectively operated depending onturbidity of the raw water.
 2. The multistage fiber filtering apparatusof claim 1, further comprising: a turbidity meter configured to measurethe turbidity of the raw water.
 3. The multistage fiber filteringapparatus of claim 2, wherein when the turbidity measured by theturbidity meter is low, the raw water is filtered by the firstfiltration mode; when the turbidity measured by the turbidity meter ismedium, the raw water is filtered by the second filtration mode; andwhen the turbidity measured by the turbidity meter is high, the rawmaterial is filtered by the third filtration mode.
 4. The multistagefiber filtering apparatus of claim 3, further comprising: a first pipeconfigured to be formed on one side wall of a lower portion of the upperbox and to introduce the raw water; a second pipe configured to beformed on one side wall of a lower portion of the lower box and todischarge filtered water; and a third pipe configured to formed on oneside wall of an upper portion of the lower box and to introduce the rawwater or discharge the filtered water.
 5. The multistage fiber filteringapparatus of claim 4, wherein in the first filtration mode, the rawwater is introduced through the third pipe to pass through the fiberball medium and then be discharged through the second pipe.
 6. Themultistage fiber filtering apparatus of claim 5, wherein in the secondfiltration mode, the raw water is introduced through the first pipe topass through the fiber yarn medium and then be discharged through thethird pipe.
 7. The multistage fiber filtering apparatus of claim 6,wherein in the third filtration mode, the raw water is introducedthrough the first pipe to sequentially pass through the fiber yarnmedium and the fiber ball medium and then be discharged through thesecond pipe.
 8. The multistage fiber filtering apparatus of claim 7,wherein the first pipe comprises: a raw water inlet pipe provided with araw water inlet control valve that controls an introduced amount of rawwater; and a backwashing water discharge pipe provided with abackwashing water discharge control valve that regulates a dischargedamount of backwashing water.
 9. The multistage fiber filtering apparatusof claim 8, further comprising: a first air inlet pipe connected to oneside of the second pipe to introduce air during backwashing.
 10. Themultistage fiber filtering apparatus of claim 9, further comprising: asecond air inlet pipe connected to one side of the third pipe tointroduce air during backwashing.
 11. The multistage fiber filteringapparatus of claim 10, further comprising: an air discharge pipe locatedon an upper surface of the upper box to discharge air.
 12. Themultistage fiber filtering apparatus of claim 7, further comprising: acontroller configured to selectively introduce the raw water into thefirst pipe or the third pipe depending on the turbidity measured by theturbidity meter.
 13. The multistage fiber filtering apparatus of claim12, wherein the controller controls the raw water to be introducedthrough the third pipe when the turbidity measured by the turbiditymeter is low turbidity and controls the raw water to be introducedthrough the first pipe when the turbidity is medium turbidity or highturbidity.
 14. The multistage fiber filtering apparatus of claim 13,wherein a part of the second pipe is provided with a second pipe controlvalve for determining a discharged amount of filtered water.
 15. Themultistage fiber filtering apparatus of claim 14, wherein a part of thethird pipe is provided with a third pipe control valve for determiningthe introduced amount of raw water or the discharged amount of filteredwater.
 16. The multistage fiber filtering apparatus of claim 15, whereinthe controller controls the third pipe control valve and the second pipecontrol valve to be open when the raw water is of low turbidity so thatthe raw water is filtered by the first filtration mode.
 17. Themultistage fiber filtering apparatus of claim 16, wherein the controllercontrols a control valve, which is located in the first pipe to regulatean introduced amount of raw water when the raw water is of mediumturbidity, and the third pipe control valve to both be open and controlsthe second pipe control valve to be closed to filter the raw water bythe second filtration mode.
 18. The multistage fiber filtering apparatusof claim 17, wherein the controller controls the control valve, which islocated in the first pipe to regulate an introduced amount of raw waterwhen the raw water is of high turbidity, and the second pipe controlvalve to both be open and controls the third control valve to be closedto filter the raw water by the third filtration mode.
 19. The multistagefiber filtering apparatus of claim 1, wherein a distribution plateprovided with a plurality of distribution grooves is installed betweenthe upper box and the lower box.
 20. The multistage fiber filteringapparatus of claim 1, wherein a lower end of the upper box is providedwith a swash plate reaching from a lower end of the strainer to an outersurface of the lower box along a circumferential direction.